EZ Math Movie, Tutorials, Turtle Graphics, What is the turtle?

A drawing robot

The turtle is an imaginary, invisible drawing robot. It is called the turtle because the very first one developed at MIT for their LOGO computer language was actually a mechanical robot that looked a bit like a salad bowl turned upside-down, and, thus, it looked a bit like a turtle. This robot had motorized wheels and propelled itself around the floor over distances and in directions commanded to it from a computer to which it was connected. The floor was covered with paper, and the turtle had a drawing pen that could be lowered to touch the paper, and so the turtle could leave a line drawn as it moved around.

How we will picture the turtle

We will picture the turtle from above as a blue rounded disk with a yellow arrow on it. The arrow shows the turtle's heading. This heading is the direction in which the turtle will move when it is given the motion command forward or back. The turtle's heading can be changed by giving it the turning command right or left. There are further explanations of these commands in the following tutorials.

A picture of the turtle

The turtle at the origin

The turtle's heading

As we shall see, the turtle can be aimed in any direction on the (x, y) graph. The direction in which it is aimed is called its heading. When the turtle is moved with the commands forward and back, it will go in the direction of its heading.

The turtle's heading in EZ Math Movie is different from the way it is handled in traditional LOGO languages. In EZ Math Movie the heading is described in a way that mimics the manner in which angles are measured when they are in standard position.
The turtle at the origin

Above are some common turtle heading in degrees.

The turtle draws while moving.

As we will see, commands such as forward and back move the turtle. By default, when the turtle moves, it draws a line along its path.

The turtle at the origin

Running the example program

This example program shows the turtle moving about. The commands used in this program will be explained in the following tutorials.

The example program

Angle measurement: Degrees Radians

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Next tutorial: Forward and back


Here is a link to a related article at EZ Programing Demos:

Turtle graphics

All contents of EZ Math Movie are copyrighted: Copyright 2011, Edward A. Zobel. All rights reserved.

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